Wide ratio transmission with four planetary gear sets

ABSTRACT

The transmission has a plurality of members that can be utilized in powertrains to provide at least eight forward speed ratios and one reverse speed ratio. The transmission includes four planetary gear sets having seven torque-transmitting mechanisms, four fixed interconnections, and a stationary (grounded) member. The powertrain includes an engine and torque converter that is selectively connected to at least one of the planetary gear members and an output member that is continuously connected with another one of the planetary gear members. The seven torque-transmitting mechanisms provide interconnections between various gear members and with the transmission housing, and are operated in combinations of two to establish at least eight forward speed ratios and at least one reverse speed ratio.

TECHNICAL FIELD

The present invention relates to a family of power transmissions havingfour planetary gear sets that are controlled by seventorque-transmitting devices to provide at least eight forward speedratios and at least one reverse speed ratio.

BACKGROUND OF THE INVENTION

Passenger vehicles include a powertrain that is comprised of an engine,multi-speed transmission, and a differential or final drive. Themulti-speed transmission increases the overall operating range of thevehicle by permitting the engine to operate through its torque range anumber of times. The number of forward speed ratios that are availablein the transmission determines the number of times the engine torquerange is repeated. Early automatic transmissions had two speed ranges.This severely limited the overall speed range of the vehicle andtherefore required a relatively large engine that could produce a widespeed and torque range. This resulted in the engine operating at aspecific fuel consumption point during cruising, other than the mostefficient point. Therefore, manually-shifted (countershafttransmissions) were the most popular.

With the advent of three- and four-speed automatic transmissions, theautomatic shifting (planetary gear) transmission increased in popularitywith the motoring public. These transmissions improved the operatingperformance and fuel economy of the vehicle. The increased number ofspeed ratios reduces the step size between ratios and therefore improvesthe shift quality of the transmission by making the ratio interchangessubstantially imperceptible to the operator under normal vehicleacceleration.

Six-speed transmissions offer several advantages over four- andfive-speed transmissions, including improved vehicle acceleration andimproved fuel economy. While many trucks employ power transmissionshaving six or more forward speed ratios, passenger cars are stillmanufactured with three- and four-speed automatic transmissions andrelatively few five or six-speed devices due to the size and complexityof these transmissions.

Seven-, eight- and nine-speed transmissions provide further improvementsin acceleration and fuel economy over six-speed transmissions. However,like the six-speed transmissions discussed above, the development ofseven-, eight- and nine-speed transmissions has been precluded becauseof complexity, size and cost.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved familyof transmissions having four planetary gear sets controlled to provideat least eight forward speed ratios and at least one reverse speedratio.

The electrically variable transmission family of the present inventionhas four planetary gear sets, each of which includes a first, second andthird member, which members may comprise a sun gear, a ring gear, or aplanet carrier assembly member, in any order.

In referring to the first, second, third and fourth gear sets in thisdescription and in the claims, these sets may be counted “first” to“fourth” in any order in the drawings (i.e., left to right, right toleft, etc.). Additionally, the first, second or third members of eachgear set may be counted “first” to “third” in any order in the drawings(i.e., top to bottom, bottom to top, etc.) for each gear set.

Each carrier member can be either a single-pinion carrier member(simple) or a double-pinion carrier member (compound).

A first interconnecting member continuously connects the first member ofthe first planetary gear set with the first member of the secondplanetary gear set and with the first member of the third planetary gearset.

A second interconnecting member continuously connects the second memberof the first planetary gear set with the second member of the thirdplanetary gear set and with the first member of the fourth planetarygear set.

A third interconnecting member continuously connects the third member ofthe first planetary gear set with the second member of the fourthplanetary gear set.

A fourth interconnecting member continuously connects the second memberof the second planetary gear set with the third member of the thirdplanetary gear set.

The input shaft is selectively connected with at least one member of theplanetary gear sets. The output shaft is continuously connected with atleast one member of the planetary gear sets.

A first torque transmitting device, such as an input clutch, selectivelyinterconnects a member of the fourth planetary gear set with the inputmember.

A second torque transmitting device, such as an input clutch,selectively connects a member of the first planetary gear set with theinput member.

A third torque transmitting device, such as a brake, selectivelyconnects a member of the fourth planetary gear set with a stationarymember (transmission housing/casing).

A fourth torque transmitting device, such as a brake, selectivelyconnects the third interconnecting member with a stationary member(transmission housing/casing).

A fifth torque transmitting device, such as a brake, selectivelyconnects the second interconnecting member with a stationary member(transmission housing/casing).

A sixth torque transmitting device, such as a brake, selectivelyconnects the fourth interconnecting member with a stationary member(transmission housing/casing).

A seventh torque transmitting device, such as a brake, selectivelyconnects a member of the second planetary gear set with a stationarymember.

The seven torque-transmitting mechanisms are selectively engageable incombinations of two to yield at least eight forward speed ratios and atleast one reverse speed ratio.

This transmission arrangement ensures that no more than one input clutchis open during operation, leading to low transmission spin losses.

A variety of speed ratios and ratio spreads can be realized by suitablyselecting the tooth ratios of the planetary gear sets.

The above features and other features and advantages of the presentinvention are readily apparent from the following detailed descriptionof the best modes for carrying out the invention when taken inconnection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a schematic representation of a powertrain including aplanetary transmission in accordance with the present invention; and

FIG. 1 b is a truth table and chart depicting some of the operatingcharacteristics of the powertrain shown in FIG. 1 a.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawing, there is shown in FIG. 1 a a powertrain 10having a conventional engine and torque converter 12, a planetarytransmission 14, and a conventional final drive mechanism 16. The engine12 may be powered using various types of fuel to improve the efficiencyand fuel economy of a particular application. Such fuels may include,for example, gasoline; diesel; ethanol; dimethyl ether; etc.

The planetary transmission 14 includes an input shaft 17 continuouslyconnected with the engine 12, a planetary gear arrangement 18, and anoutput shaft 19 continuously connected with the final drive mechanism16. The planetary gear arrangement 18 includes four planetary gear sets20, 30, 40 and 50.

The planetary gear set 20 includes a sun gear member 22, a ring gearmember 24, and a planet carrier assembly member 26. The planet carrierassembly member 26 includes a plurality of pinion gears 27 rotatablymounted on a carrier member 29 and disposed in meshing relationship withboth the sun gear member 22 and the ring gear member 24.

The planetary gear set 30 includes a sun gear member 32, a ring gearmember 34, and a planet carrier assembly member 36. The planet carrierassembly member 36 includes a plurality of pinion gears 37, 38 rotatablymounted on a carrier member 39. The pinion gears 37 are disposed inmeshing relationship with the ring gear member 34. The pinion gears 38are disposed in meshing relationship both the sun gear member 32 and therespective pinion gear 37.

The planetary gear set 40 includes a sun gear member 42, a ring gearmember 44, and a planet carrier assembly member 46. The planet carrierassembly member 46 includes a plurality of pinion gears 47, 48 rotatablymounted on a carrier member 49. The pinion gears 47 are disposed inmeshing relationship with the ring gear member 44. The pinion gears 48are disposed in meshing relationship with both the sun gear member 42and the respective pinion gear 47.

The planetary gear set 50 includes a sun gear member 52, a ring gearmember 54 and a planet carrier assembly member 56. The planet carrierassembly member 56 includes a plurality of pinion gears 57 rotatablymounted on a carrier member 59 and disposed in meshing relationship withboth the sun gear member 52 and the ring gear member 54.

The planetary gear arrangement also includes seven torque-transmittingmechanisms 80, 82, 84, 85, 86, 87 and 88. The torque-transmittingmechanisms 80 and 82 are rotating-type torque-transmitting mechanisms,commonly termed clutches. The torque-transmitting mechanisms 84, 85, 86,87 and 88 are stationary-type torque-transmitting mechanisms, commonlytermed brakes or reaction clutches.

The output shaft 19 is continuously connected with the ring gear member24. The first interconnecting member 70 continuously connects the ringgear member 24 of the planetary gear set 20 with the sun gear member 32of the planetary gear set 30 and with the ring gear member 44 of theplanetary gear set 40. A second interconnecting member 72 continuouslyconnects the planet carrier assembly member 26 of the planetary gear set20 with the sun gear member 42 of the planetary gear set 40 and with thering gear member 54 of the planetary gear set 50. A thirdinterconnecting member 74 continuously connects the sun gear member 22of the planetary gear set 20 with the planet carrier assembly member 56of the planetary gear set 50. A fourth interconnecting member 76continuously connects the ring gear member 34 of the planetary gear set30 with the planet carrier assembly member 46 of the planetary gear set40.

A first torque transmitting device, such as clutch 80, selectivelyconnects the planet carrier assembly member 56 with the input member 17.A second torque transmitting device, such as clutch 82, selectivelyconnects the planet carrier assembly member 26 with the input member. Athird torque transmitting device, such as brake 84, selectively connectsthe sun gear member 52 with the transmission housing 60. A fourth torquetransmitting device, such as brake 85, selectively connects the sun gearmember 22 and the planet carrier assembly member 56 via interconnectingmember 74 with the transmission housing 60. A fifth torque transmittingdevice, such as brake 86, selectively connects the planet carrierassembly member 26, sun gear member 42 and the ring gear member 54 viainterconnecting member 72 with the transmission housing 60. A sixthtorque transmitting device, such as brake 87, selectively connects thering gear member 34 and the planet carrier assembly member 46 viainterconnecting member 76 with the transmission housing 60. A seventhtorque transmitting device, such as brake 88, selectively connects theplanet carrier assembly member 36 with the transmission housing 60.

As shown in FIG. 1 b, and in particular the truth table disclosedtherein, the torque-transmitting mechanisms are selectively engaged incombinations of two to provide eight forward speed ratios and tworeverse speed ratios.

The reverse (Reverse) speed ratio is established with the engagement ofthe input clutch 80 and the brake 89. The input clutch 80 connects thesun gear member 22 and the planet carrier assembly member 56 viainterconnecting member 74 with the input member 17. The brake 86connects the planet carrier assembly member 26, the sun gear member 42and the ring gear member 54 via interconnecting member 72 with thetransmission housing 60. The sun gear member 22 and the planet carrierassembly member 26 rotate at the same speed as the input member 17. Theplanet carrier assembly member 26, sun gear member 42 and ring gearmember 54 do not rotate. The ring gear member 24, sun gear member 32 andring gear member 44 rotate at the same speed as the output member 19.The ring gear member 44 rotates at a speed determined by the speed ofthe planet carrier assembly member 46 and the ring gear/sun gear toothratio of the planetary gear set 40. The ring gear member 24, andtherefore the output member 19, rotates at a speed determined from thespeed of the sun gear member 22 and the ring gear/sun gear tooth ratioof the planetary gear set 20. The numerical value of the reverse speedratio is determined utilizing the ring gear/sun gear tooth ratios of theplanetary gear sets 20 and 40.

The first forward speed ratio is established with the engagement of theinput clutch 80, and the brake 87. The input clutch 80 connects the sungear member 22 and the planet carrier assembly member 56 viainterconnecting member 74 with the input member 17. The brake 87connects the ring gear member 34 and the planet carrier assembly member46 via interconnecting member 76 with the transmission housing 60. Thesun gear member 22 and planet carrier assembly member 56 rotate at thesame speed as the input member 17. The ring gear member 34 and planetcarrier assembly member 46 do not rotate. The planet carrier assemblymember 26, sun gear member 42 and ring gear member 54 rotate at the samespeed. The speed of the sun gear member 42 is determined from the speedof the ring gear member 44 and the ring gear/sun gear tooth ratio of theplanetary gear set 40. The ring gear member 24, sun gear member 32 andring gear member 44 rotate at the same speed as the output member 19.The speed of the ring gear member 24, and therefore the output member19, is determined from the speed of the sun gear member 22, the speed ofthe planet carrier assembly member 26 and the ring gear/sun gear toothratio of the planetary gear set 20. The numerical value of the firstforward speed ratio is determined utilizing the ring gear/sun gear toothratios of the planetary gear sets 20 and 40.

The second forward speed ratio is established with the engagement of theinput clutch 80 and the brake 88. The input clutch 80 connects the sungear member 22 and the planet carrier assembly member 56 with the inputmember 17. The brake 88 connects the planet carrier assembly member 36with the transmission housing 60. The sun gear member 22 and the planetcarrier assembly member 56 rotate at the same speed as the input member17. The planet carrier assembly member 26, sun gear member 42 and ringgear member 54 rotate at the same speed. The sun gear member 42 rotatesat a speed determined from the speed of the ring gear member 44, thespeed of the planet carrier assembly member 46 and the ring gear/sungear tooth ratio of the planetary gear set 40. The ring gear member 24,sun gear member 32 and ring gear member 44 rotate at the same speed asthe output member 19. The speed of the ring gear member 24, andtherefore the output member 19, is determined from the speed of the sungear member 22, the speed of the planet carrier assembly member 26 andthe ring gear/sun gear tooth ratio of the planetary gear set 20. Thenumerical value of the second forward speed ratio is determinedutilizing the ring gear/sun gear tooth ratios of the planetary gear sets20, 30 and 40.

The third forward speed ratio is established with the engagement of theinput clutch 82 and brake 87. The input clutch 82 connects the planetcarrier assembly member 26, sun gear member 42 and ring gear member 54with the input member 17. The brake 87 connects the ring gear member 34and planet carrier assembly member 46 with the transmission housing 60.The planet carrier assembly member 26, sun gear member 42 and ring gearmember 54 rotate at the same speed as the input member 17. The ring gearmember 34 and planet carrier assembly member 46 do not rotate. The ringgear member 24, sun gear member 32 and ring gear member 44 rotate at thesame speed as the output member 19. The speed of the ring gear member 44is determined from the speed of the sun gear member 42 and the ringgear/sun gear tooth ratio of the planetary gear set 40. The speed of thering gear member 24, and therefore the output member 19, is determinedfrom the speed of the sun gear member 22, the speed of the planetcarrier assembly member 26 and the ring gear/sun gear tooth ratio of theplanetary gear set 20. The numerical value of the third forward speedratio is determined utilizing the ring gear/sun gear tooth ratios of theplanetary gear sets 20 and 40.

The fourth forward speed ratio is established with the engagement of theinput clutch 82 and the brake 88. The input clutch 82 connects theplanet carrier assembly member 26 and the sun gear member 42 with theinput member 17. The brake 88 connects the planet carrier assemblymember 36 with the transmission housing 60. The planet carrier assemblymember 26, sun gear member 42 and ring gear member 54 rotate at the samespeed as the input member 17. The sun gear member 22 and planet carrierassembly member 56 rotate at the same speed. The ring gear member 34 andplanet carrier assembly member 46 rotate at the same speed. The speed ofthe planet carrier assembly member 46 is determined from the speed ofthe sun gear member 42, the speed of the ring gear member 44 and thering gear/sun gear tooth ratio of the planetary gear set 40. The planetcarrier assembly member 36 does not rotate. The speed of the sun gearmember 32 is determined from the speed of the ring gear member 34 andthe ring gear/sun gear tooth ratio of the planetary gear set 30. Thering gear member 24, sun gear member 32 and ring gear member 42 rotateat the same speed as the output member 19. The speed of the ring gearmember 24, and therefore the output member 19, rotates at a speeddetermined from the speed of the sun gear member 22, the speed of theplanet carrier assembly member 26 and the ring gear/sun gear tooth ratioof the planetary gear set 20. The numerical value of the fourth forwardspeed ratio is determined utilizing the ring gear/sun gear tooth ratioof the planetary gear sets 20, 30 and 40.

The fifth forward speed ratio is established with the engagement of theinput clutches 80 and 82. In this configuration, the input shaft 17 isdirectly connected with the output shaft 19. The numerical value of thefifth forward speed ratio is 1.

The sixth forward speed ratio is established with the engagement of theinput clutch 82 and the brake 84. The input clutch 82 connects theplanet carrier assembly member 26, the sun gear member 42 and ring gearmember 54 with the input member 17. The brake 84 connects the sun gearmember 52 with the transmission housing 60. The sun gear member 52 doesnot rotate. The planet carrier assembly member 26, sun gear member 42and ring gear member 54 rotate at the same speed as the input member 17.The sun gear member 22 and planet carrier assembly member 56 rotate atthe same speed. The speed of the planet carrier assembly member 56 isdetermined from the speed of the ring gear member 54 and the ringgear/sun gear tooth ratio of the planetary gear set 50. The ring gearmember 34 and planet carrier assembly member 46 rotate at the samespeed. The speed of the planet carrier assembly member 46 is determinedfrom the speed of the ring gear member 44, the speed of the sun gearmember 42 and the ring gear/sun gear tooth ratio of the planetary gearset 40. The ring gear member 24, sun gear member 32 and ring gear member44 rotate at the same speed as the output member 19. The speed of thering gear member 24, and therefore the output member 19, is determinedfrom the speed of the sun gear member 24, the speed of the planetcarrier assembly member 26 and the ring gear/sun gear tooth ratio of theplanetary gear set 20. The numerical value of the sixth forward speedratio is determined utilizing the ring gear/sun gear tooth ratios of theplanetary gear sets 20, 40 and 50.

The seventh forward speed ratio is established with the engagement ofthe input clutch 82 and the brake 85. The input clutch 82 connects theplanet carrier assembly member 26, sun gear member 42 and ring gearmember 54 with the input member 17. The brake 85 connects the sun gearmember 22 and planet carrier assembly member 56 with the transmissionhousing 60. The sun gear member 22 and planet carrier assembly member 56do not rotate. The planet carrier assembly member 26, sun gear member 42and ring gear member 54 rotate at the same speed as the input member 17.The ring gear member 24, sun gear member 32 and ring gear member 44rotate at the same speed as the output member 19. The ring gear member34 and planet carrier assembly member 46 rotate at the same speed. Thespeed of the planet carrier assembly member 46 is determined from thespeed of the sun gear member 42, the speed of the ring gear member 44and the ring gear/sun gear tooth ratio of the planetary gear set 40. Thespeed of the ring gear member 24, and therefore the output member 19, isdetermined from the speed of the planet carrier assembly member 26 andthe ring gear/sun gear tooth ratio of the planetary gear set 20. Thenumerical value of the seventh forward speed ratio is determinedutilizing the ring gear/sun gear tooth ratios of the planetary gear sets20 and 40.

The eighth forward speed ratio is established with the engagement of theinput clutch 80 and the brake 84. The input clutch 80 connects the sungear member 22 and the planet carrier assembly member 56 with the inputmember 17. The brake 84 connects the sun gear member 52 with thetransmission housing 60. The sun gear member 52 does not rotate. The sungear member 22 and planet carrier assembly member 56 rotate at the samespeed as the input member 17. The planet carrier assembly member 26, sungear member 42 and ring gear member 54 rotate at the same speed. Thespeed of the ring gear member 54 is determined from the speed of theplanet carrier assembly member 56 and the ring gear/sun gear tooth ratioof the planetary gear set 50. The ring gear member 34 and planet carrierassembly member 46 rotate at the same speed. The ring gear member 24 sungear member 32 and ring gear member 44 rotate at the same speed as theoutput member 19. The speed of the ring gear member 44 is determinedfrom the speed of the sun gear member 42, the speed of the planetcarrier assembly member 46 and the ring gear/sun gear tooth ratio of theplanetary gear set 40. The speed of the ring gear member 24, andtherefore the output member 19, is determined from the speed of the sungear member 22, the speed of the planet carrier assembly member 26 andthe ring gear/sun gear tooth ratio of the planetary gear set 20. Thenumerical value of the eighth forward speed ratio is determinedutilizing the ring gear/sun gear tooth ratio of the planetary gear sets20, 40 and 50.

As set forth above, the engagement schedule for the torque-transmittingmechanisms is shown in the truth table of FIG. 1 b. This truth tablealso provides an example of speed ratios that are available utilizingthe ring gear/sun gear tooth ratios given by way of example in FIG. 1 b.The N_(R1)/S_(R1) value is the tooth ratio of the planetary gear set 20;the N_(R2)/S_(R2) value is the tooth ratio of the planetary gear set 30;and the N_(R3)/S_(R3) value is the tooth ratio of the planetary gear set40. Also, the chart of FIG. 1 b describes the ratio steps that areattained utilizing the sample of tooth ratios given. For example, thestep ratio between the first and second forward speed ratios is 1.64,while the step ratio between the reverse speed ratio (Reverse) and firstforward ratio is −0.56. It should be noted that the single step forwardratio interchanges are of the single transition variety.

The powertrain 10 may share components with a hybrid vehicle, and such acombination may be operable in a “charge-depleting mode”. For purposesof the present invention, a “charge-depleting mode” is a mode whereinthe vehicle is powered primarily by an electric motor/generator suchthat a battery is depleted or nearly depleted when the vehicle reachesits destination. In other words, during the charge-depleting mode, theengine 12 is only operated to the extent necessary to ensure that thebattery is not depleted before the destination is reached. Aconventional hybrid vehicle operates in a “charge-sustaining mode”,wherein if the battery charge level drops below a predetermined level(e.g., 25%) the engine is automatically run to recharge the battery.Therefore, by operating in a charge-depleting mode, the hybrid vehiclecan conserve some or all of the fuel that would otherwise be expended tomaintain the 25% battery charge level in a conventional hybrid vehicle.It should be appreciated that a hybrid vehicle powertrain is preferablyonly operated in the charge-depleting mode if the battery can berecharged after the destination is reached by plugging it into an energysource.

While the best modes for carrying out the invention have been describedin detail, those familiar with the art to which this invention relateswill recognize various alternative designs and embodiments forpracticing the invention within the scope of the appended claims.

1. A multi-speed transmission comprising: an input shaft; an outputshaft; first, second, third and fourth planetary gear sets each havingfirst, second and third members; said input shaft being selectivelyconnectable with at least one member of said planetary gear sets, andsaid output shaft being continuously interconnected with another memberof said planetary gear sets; a first interconnecting member continuouslyconnecting said first member of said first planetary gear set with saidfirst member of said second planetary gear set and said first member ofsaid third planetary gear set; a second interconnecting membercontinuously connecting said second member of said first planetary gearset with said second member of said third planetary gear set and saidfirst member of said fourth planetary gear set; a third interconnectingmember continuously connecting said third member of said first planetarygear set with said second member of said fourth planetary gear set; afourth interconnecting member continuously connecting said second memberof said second planetary gear set with said third member of said thirdplanetary gear set; a first torque-transmitting mechanism selectivelyconnecting a member of said fourth planetary gear set with said inputmember; a second torque-transmitting mechanism selectively connecting amember of said first planetary gear set with said input member; a thirdtorque-transmitting mechanism selectively connecting a member of saidfourth planetary gear set with a stationary member; a fourthtorque-transmitting mechanism selectively connecting said thirdinterconnecting member with said stationary member; a fifthtorque-transmitting mechanism selectively connecting said secondinterconnecting member with said stationary member; a sixthtorque-transmitting mechanism selectively connecting said fourthinterconnecting member with said stationary member; a seventhtorque-transmitting mechanism selectively connecting a member of saidsecond planetary gear set with said stationary member; saidtorque-transmitting mechanisms being engaged in combinations of two toestablish at least eight forward speed ratios and at least one reversespeed ratio between said input shaft and said output shaft.
 2. Thetransmission defined in claim 1, wherein said first and secondtorque-transmitting mechanisms comprise clutches, and said third,fourth, fifth, sixth and seventh torque-transmitting mechanisms comprisebrakes.
 3. The transmission defined in claim 1, wherein at least oneplanet carrier assembly member of said planetary gear sets is adouble-pinion carrier.
 4. A multi-speed transmission comprising: aninput shaft; an output shaft; a planetary gear arrangement having first,second, third and fourth planetary gear sets, each planetary gear sethaving first, second and third members; said input shaft beingselectively connectable with at least one member of said planetary gearsets, and said output shaft being continuously interconnected withanother member of said planetary gear sets; a first interconnectingmember continuously connecting said first member of said first planetarygear set with said first member of said second planetary gear set andsaid first member of said third planetary gear set; a secondinterconnecting member continuously connecting said second member ofsaid first planetary gear set with said second member of said thirdplanetary gear set and said first member of said fourth planetary gearset; a third interconnecting member continuously connecting said thirdmember of said first planetary gear set with said second member of saidfourth planetary gear set; a fourth interconnecting member continuouslyconnecting said second member of said second planetary gear set withsaid third member of said third planetary gear set; and seventorque-transmitting mechanisms for selectively interconnecting saidmembers of said planetary gear sets with said stationary member or withother members of said planetary gear sets, said seventorque-transmitting mechanisms being engaged in combinations of two toestablish at least eight forward speed ratios and at least one reversespeed ratio between said input shaft and said output shaft.
 5. Thetransmission defined in claim 4, wherein a first of said seventorque-transmitting mechanisms is operable for selectively connecting amember of said fourth planetary gear set with said input member.
 6. Thetransmission defined in claim 5, wherein a second of said seventorque-transmitting mechanisms is operable for selectively connecting amember of said first planetary gear set with said input member.
 7. Thetransmission defined in claim 6, wherein a third of said seventorque-transmitting mechanisms is operable for selectively connecting amember of said fourth planetary gear set with said stationary member. 8.The transmission defined in claim 7, wherein a fourth of said seventorque-transmitting mechanisms is operable for selectively connectingsaid third interconnecting member with said stationary member.
 9. Thetransmission defined in claim 8, wherein a fifth of said seventorque-transmitting mechanisms is operable for selectively connectingsaid second interconnecting member with said stationary member.
 10. Thetransmission defined in claim 9, wherein a sixth of said seventorque-transmitting mechanisms is operable for selectively connectingsaid fourth interconnecting member with said stationary member.
 11. Thetransmission defined in claim 10, wherein a seventh of said seventorque-transmitting mechanisms is operable for selectivelyinterconnecting a member of said second planetary gear set with saidstationary member.
 12. The transmission defined in claim 5, wherein atleast one planet carrier assembly member of said planetary gear sets isa double-pinion carrier.